Open and enclosed photobioreactors comparison in terms of organic matter utilization, biomass chemical profile and photosynthetic efficiency

Microalgae systems are currently being researched due to their ability to mitigate carbon dioxide emissions while obtaining a value-added product in the form of biomass. This paper elucidates the ability of microalgal–bacteria consortia for the conversion of organic matter contained in anaerobically digested swine slurry into biomass organic carbon via CO2 uptake. In this context, the configuration of the reactor, different nitrogen availabilities and different microalgal communities developed in the evaluated reactors (open pond and enclosed tubular photobioreactor) were inferred as a possible reason for the different conversion efficiencies found. The biomass quality in terms of macromolecular cell component obtained under the two different reactors did not show any clear difference. The high efficiency in biomass nitrogen uptake resulted in biomass mainly composed of carbohydrates and proteins. Finally, the photosynthetic efficiency of the two reactor types showed high values which indicated the high efficiency of converting irradiance supplied to the systems into energy stored in biomass.